1. Technical Field
The present invention relates to a liquid-crystal display device provided with liquid crystals and to an electronic apparatus including the liquid-crystal display device provided with liquid crystals.
2. Description of the Related Art
There have been developed systems (modes) for driving liquid crystals, including a liquid crystal driving system that uses an electric field generated in a vertical direction between substrates, that is, a vertical electric field. Examples of a liquid crystal display device that drives liquid crystals using a vertical electric field include, but are not limited to, vertical-electric-field liquid crystal display devices provided with a twisted nematic (TN) system, a vertical alignment (VA) system, an electrically controlled birefringence (ECB) system, etc. As disclosed in Japanese Patent Application Laid-open Publication No. 2008-52161 (JP-A-2008-52161), there has also been developed a liquid crystal driving system that uses an electric field generated in a direction parallel to substrates (horizontal direction), that is, a horizontal electric field. Examples of a liquid crystal display device that drives liquid crystals using a horizontal electric field include, but are not limited to, horizontal-electric-field liquid crystal display devices provided with a fringe field switching (FFS) system, an in-plane switching (IPS) system, etc.
In the IPS mode, a first electrode and a second electrode are provided on the same layer, and an electric field is generated mainly in a direction parallel to the substrate surface. This configuration makes it difficult for the electric field to be generated in an area on the first electrode, thereby making it difficult for liquid-crystal molecules in the area to be driven.
In the FFS mode, a pixel electrode and a common electrode overlap in a direction perpendicular to the substrate surface with a dielectric film interposed therebetween, and an electric field extending mainly in a direction oblique to the substrate surface or a parabolic electric field (also referred to as a fringe electric field) is generated. This makes it easy for liquid-crystal molecules in an area on the pixel electrode to be driven. In other words, the FFS mode can provide a higher aperture ratio than the IPS mode does.
The horizontal-electric-field liquid crystal display device generates an electric field between the first electrode and the second electrode in a direction parallel to the substrate, thereby rotating the liquid crystal molecules in a plane parallel to the substrate surface. The liquid crystal display device uses a change in the light transmittance corresponding to the rotation of the liquid crystal molecules, thereby performing display. Such horizontal-electric-field liquid crystal display devices are required to achieve a higher response speed of the liquid crystals.
Japanese Patent Application Laid-open Publication No. 2013-109309 (JP-A-2013-109309) discloses a liquid crystal display device achieving a higher response speed of liquid crystals.
In the liquid crystal display device disclosed in JP-A-2013-109309, although the response speed of the liquid crystals is improved in the whole pixels, there is an area in which the liquid crystal molecule hardly move even when voltage is applied, and improvement in contrast is desired.
For the foregoing reasons, there is a need for a liquid crystal display device and an electronic apparatus that improve the contrast of entire pixels while improving the response speed of the entire pixels to further improve display quality in a plane.